Presently used steel bridge fabrication involves splicing together individual girders in order to create longer length bridge spans. Girders are joined together with splice plates that are bolted to each girder through holes near the ends of the girders. Girders have holes in the top and bottom flanges and in the web. Typical bridge girders may have hundreds of holes in a single splice connection.
One current fabrication practice for making the holes for the splice connection involves a match-drilling process. Referring to FIG. 1, one form of match-drilling is known as the lay down process. Girders 1 and 2 are fabricated initially with no splice holes. A pair of girders 1 and 2 to be joined with splice plates are laid on their side and manually aligned based on a string-line reference placed on a shop floor. Once aligned, splice plates with full-sized holes already in the plates are clamped to the girder pair and used as a template to match-drill the holes in both girders. This lay down process is used to make sure that all holes in the girder are in alignment with the holes in the plates.
There are variations on the process, such as the sub-drill and ream process, both collectively referred to herein as “match-drilling.” This latter match-drilling process pre-drills holes in the girder smaller than the final hole diameter during fabrication of the girders. Two girders to be joined together are then blocked in an upright position and aligned. Once aligned, splice plates with full-sized holes already in the plates are clamped or pinned in the girder pair and used as a template to ream all holes in the girders to their final size. As with the lay down process, this sub-drill and ream process is used to make sure that all holes in the girder are in alignment with the holes in the splice plate.
These processes of match-drilling splice plate holes have the benefit of guaranteed hole alignment in the girders and splice plates. However, these processes are very time-consuming and expensive. Some estimates put the cost of this step in the fabrication process at 15% to 20% of the cost of a steel bridge. Additionally, match-drilling holes at the end of the fabrication process requires multiple drills at different orientations, or the repositioning of drills, and drilling on a fabricated girder, i.e. a girder where the girder flanges have been welded to a girder web. Match-drilling is, therefore, much more difficult than drilling on a flat plate.
The match-drilling processes also take up considerable floor space in the shop. Depending on the shop, the laydown area may require one-third to one-half of the floor space of the entire shop. Girders are laid on their sides and set end to end, taking up several hundred feet of space. Curved girders when set on their sides need to be appropriately blocked and can be more difficult to work with as they extend high off the shop floor.
The current apparatus and methods for bridge fabrication, therefore, have various shortcomings, including, for example, those noted above. Accordingly, there is a need in the bridge fabrication industry for a simple and less expensive means to fabricate splice plates and to generate, store and report data for as-fabricated girders and girder assembly.